Aussie swimming great Cate Campbell has Karl Stefanovic in stitches with joke about a stunning gender detail at the Paris Olympics

Aussie swimming legend Cate Campbell left host Karl Stefanovic in stitches on live television after she cracked a joke about a stunning gender detail from the Paris Olympics.

Speaking on Channel Nine after Dolphins quartet Mollie O'Callaghan, Lani Pallister, Brianna Throssell and Ariarne Titmus combined to win the 4x200m freestyle relay, Campbell pointed out a remarkable statistic - all of Australia's gold medal winners at the Games so far have been women.

'There is a theme when it comes to the Australian Olympic team at the moment,' Campbell began.

'Apparently at the moment if you want to win an Olympic gold medal you have to have a uterus.'

Stefanovic burst out laughing at Campbell's cheeky one-liner - but she wasn't finished.

'Cam McEvoy, he will swim in the 50m freestyle final,' she said. 

'He is hoping to break that theme... but he doesn't have the right anatomy at the moment.'

Campbell then repeated the gender gold medal gag in a later interview with Ben Fordham on 2GB Radio - and declared the girls are 'delivering in spades, they are on fire in the pool'.

And moments after winning the 4x200m freestyle relay, the triumphant Aussie quartet rubbed shoulders with royalty.

Queen Mary of Denmark - the Tasmania-born royal who is distantly related to Ariarne Titmus - was on hand to see the race at the La Defense Arena.

She then celebrated with the elated Aussie stars when they came to the stands to embrace family and friends.

Shortly before the Games began, Titmus revealed, 'We are actually cousins in a distant, roundabout sort of way.

'One of dad's cousins is married to Mary's cousin, which is actually pretty funny.'

Queen Mary also shared a warm embrace with O'Callaghan and took photos of the gold medallists, with Campbell noting on Channel Nine's coverage all the usual royal protocols of curtsying and shaking hands went out the window amid the excitement.

Titmus, 23, who also won the 400m freestyle, has two golds in Paris and four gold medals in her impressive Olympic career.

'I had Moll [O'Callaghan] saying some stern words in my ear behind the block, but I'm really proud of this group,' Titmus said after the relay win.

'We've wanted this [for a long time]. I was disappointed with how I swam in Tokyo, I personally felt like I let the team down, so this was a bit of a personal vendetta for me to come back and really play my role in the team, but also do it for our country.'

After winning its fifth Olympic gold in the pool, Australia also edged ahead of bitter rivals the United States on the swimming medal tally.

The US have risen to second overall in the standings behind China, with nine gold medals compared to Australia's eight.